In certain applications, parts composed primarily of composite materials have significant advantages. A composite airplane wing, for example, can provide twice the life of a conventional metal wing with no increased weight, and, at the same time, provide increased operational capabilities.
Composite parts are fabricated using several layers of composite materials, or plies, that are assembled and cured to form a laminate. The composite material is commonly a fabric or tape that is comprised of fibers having a common orientation. Each layer of this material will have a set fiber orientation along an orientation axis with structural properties that vary in accordance with the relationship to the orientation axis.
The designer of a composite part can combine layers of this material in defined orientations to produce the desired structural properties for the part. Additional layers of material can be added at locations requiring increased strength and the layers can be oriented to maximize resistance in critical load directions.
Thus, each ply of material has several attributes that must be specified by the designer;
(1) the geometric boundary or perimeter shape of the ply must be defined;
(2) the orientation of the fibers for each ply must be defined;
(3) the position of the ply with respect to the other plies in the part (sometimes called the "stacking position") must be defined. A composite part, such as an airplane wing segment, for example, may be defined by more than 2,000 unique plies.
The design of composite parts is much more complex than designing parts to be fabricated from a homogeneous material, such as metal. Currently, the time required to design, iterate, analyze and program composite parts for fabrication is very high. Because of this complexity, neither human intervention nor manual input can assure that the part will be manufactured as designed.